1. Field of the Invention
This invention relates to telecommunications networks. More particularly, the invention relates to malfunction treatments on SS7/ISDN networks for failed calls.
2. Description of Prior Art
In telecommunications networks, calls are established from source to destination, in the form of links traversing a series of switching nodes. Under normal circumstances, when the calls are terminated the links between each switching node are released in order to allow other calls to use those links. Sometimes during the process of establishing the links between the nodes, abnormal conditions are encountered which interfere with the normal creation of links from source to destination. At such times, some of the links have been established, but others of the links have not yet been established. It is then necessary to decide whether to continue establishing the remaining links, or to release all links that have so far been created and thereby completely terminate the call. Typical abnormal conditions that may be encountered are ALL TRUNKS BUSY, USER BUSY, DESTINATION OUT OF SERVICE, NETWORK OUT OF ORDER, CALL REJECTED, INFORMATION MISSING, and so forth.
The existence of normal and abnormal conditions is indicated in the telecommunication network by digital code numbers ("cause codes") that may be propagated backward along the existing links to the source or sent to centralized billing or network diagnostic stations. Often, the telecommunication network comprises a variety of vendors each generating a variety of cause codes to indicate the same conditions. It is necessary to translate the cause codes of one vendor to the codes of another vendor in order to ensure proper communication between the switching nodes.
Prior methods for managing the diversity of cause codes that may be present in the telecommunication network and for deciding which action to take upon appearance of a particular cause code have been based on hard-encoded computer programs that are difficult to create or modify when the codes change or new codes need to be added or new vendors come on-line.
The prior art related to the problems solved by the present invention include the following:
U.S. Pat. No. 5,390,242 issued Feb. 14, 1995 discloses a protocol message which is a redirect message in a telecommunications system having a number of switching nodes. The redirect message redirects a call back to a switching nodes and indicates in that message to which the switching node the call pass should be extended. In response to the redirect message, the intermediate switching node reroutes the call path. The redirect message may also entirely remove the call path between the switching node and an intermediate switching node.
In U.S. Pat. No. 4,873,687 issued Oct. 10, 1989, a method and apparatus detect and analyze errors in a communications system. The method employs an expert system techniques to isolate failures to a specific field replaceable units and attempts to restore the failing unit to service by removing it from service, resetting the resource and returning it to service if it passes retesting.
U.S. Pat. No. 4,991,204, issued Feb. 5, 1991, discloses a telecommunication network in which a switching node assigns one or more alternate routes in advance for a call. The switching node responds to a call connection request to try to connect the call to the first route, and when having failed at a call connection, the switching node retrys the call connection through one of the assigned routes.
U.S. Pat. No. 4,284,852 issued Aug. 18, 1981, discloses a alternate routing scheme for telephone system wherein a plurality of switching offices are grouped into a cluster, with each switching office in the cluster having direct trunks lines to all of the other switching offices in the cluster. Suitable equipment monitors the busy status of all the switching offices in the cluster and determines a most likely alternate routing scheme for switching office. The alternate routing scheme for each particular switching office is stored at that particular office and is periodically updated, by suitable equipment, so as to account for changes in the busy status of the other switching offices and trunk lines in the cluster.
U.S. Pat. No. 5,182,744 issued Jan. 26, 1993 discloses a restoration system for enhancing the reliability of a telecommunication network such that particular traffic which is disrupted by, for example, a faulty link, may be quickly rerouted by an alternate route established "on the fly". Each node and link forming the network is monitored, and in the event of such monitoring, detects a faulty link or node then, then a central controller is notified. The controller is arranged to locate spare capacity and establish an alternate route, in which the continuity of the alternate route is confirmed before the disruptive traffic is transferred.
U.S. Pat. No. 5,319,632 issued Jun. 7, 1994, discloses a unit specifying circuit which specifies a first and second specified unit in a cross-connect systems in accordance with a particular route which is selected as a path. When a failure occurs in a particular point of that path, the first specified unit executes a pre-determined operation in cooperation with a second specified unit. When the pre-determined operation finishes, each of the cross-connect systems is operable to select, as the path, another one of the communications route. A failure in the system is detected in accordance with a path alarm indication signal which is supplied from the particular point to each of the first and second specified unit.
None of the prior art addresses various processing scenarios which will activate an action table for release or disconnect of a call with a cause message received over a terminating SS7 or ISDN trunk unit without recoding a control program. Nor does the prior art address the problem of an interchange carrier determining which network and switch should apply a treatment and announcement for a failed call on an SS7 or ISDN network.